1. Field
The disclosed technology relates to a luminance control method of a display device, and a display device using the same. More particularly, the technology relates to a driving method for luminance control in an organic light emitting diode (OLED) display and a display device employing the same.
2. Description of the Related Technology
In recent years, various flat panel displays having weight and volume as compared with a cathode ray tube have been developed. A flat panel display may, for example, be a liquid crystal display (LCD), a field emission display (FED), a plasma display panel (PDP), or an organic light emitting diode (OLED) display.
An organic light emitting diode display refers to a flat display device using an electro-luminescence phenomenon of an organic material in an organic light emitting diode. The organic light emitting diode emits light when electrons and holes are injected from electrodes and the injected electrons and holes recombine.
The organic light emitting diode display has reduced volume and weight at least because an additional light source is not required. Such a display may be used in an electronic product such as a portable terminal or a large-sized television with advantages of high luminance and high-speed reaction.
In general, most data displayed in a large-sized organic light emitting diode display has significantly low luminance compared to the maximum luminance that can be displayed in the organic light emitting diode display. When the organic light emitting diode display is continuously operated at levels near the maximum luminance, the life span of the organic light emitting diode is shortened due to an excessive amount of driving current. Thus, unlike a liquid crystal display device, a large-sized organic light emitting diode display benefits from luminance control to reduce luminance by controlling a driving current of the organic light emitting diode.
In general, to compensate for scattering or deviation in a display module of the display, a luminance table formed of pre-set gamma data for generating several luminance steps and gray levels corresponding to luminance is provided and gamma data compensated by performing interpolation on the pre-set gamma data is continuously calculated by applying a predetermined compensation equation to control luminance such that compensation corresponding to the controlled luminance step is performed.
However, the interpolation of the pre-set gamma data is linear in a high gray level region and is non-linear in a low gray level region due to the characteristics of the organic light emitting diode display, and therefore, when the interpolation is applied at once, an optical characteristic becomes instable and inconsistent over the entire gray level range, thereby causing deterioration of image quality.
Further, the gamma data interpolation usually sets a reference luminance level to the highest luminance level, and thus the life-span of the diodes may be shortened, and particularly, a variation amount of an optical characteristic in a low gray level region of which a luminance level is low cannot be easily predicted or duplicated. An organic material of a light emission element of the display device may be changed for use with a low temperature poly-silicon (LTPS) process or process scattering and thus a variation amount of the optical characteristic becomes further difficult to predict in a lower gray level region, and accordingly work efficiency for compensation of the luminance scattering significantly suffers and luminance scattering or deviation cannot be compensated in the lowest luminance level.
Thus, luminance-specific non-uniformity needs to be improved by developing a luminance control method in a low luminance region, and a luminance compensation method of a display device to prevent life-span deterioration of the diode material of an organic light emitting element in luminance control is desirable.
The above information disclosed in this Background section is only for enhancement of understanding of the background of the invention and therefore it may contain information that does not form the prior art that is already known in this country to a person of ordinary skill in the art.